Muk's first battle was in ''[[EP077|The Fourth Round Rumble]]'', where it was selected for use in the [[Indigo Plateau Conference]]. After [[Jeanette Fisher]]'s high-level {{p|Bellsprout}} had trounced {{AP|Bulbasaur}} and {{AP|Pikachu}}, Muk made a surprise appearance as Ash's third Pokémon. Muk easily absorbed Bellsprout's physical moves and {{m|Razor Leaf}} and then simply smothered Bellsprout with {{m|Body Slam}}, winning the match for Ash.

Muk's first battle was in ''[[EP077|The Fourth Round Rumble]]'', where it was selected for use in the [[Indigo Plateau Conference]]. After [[Jeanette Fisher]]'s high-level {{p|Bellsprout}} had trounced {{AP|Bulbasaur}} and {{AP|Pikachu}}, Muk made a surprise appearance as Ash's third Pokémon. Muk easily absorbed Bellsprout's physical moves and {{m|Razor Leaf}} and then simply smothered Bellsprout with {{m|Body Slam}}, winning the match for Ash.

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===Orange Islands===

Muk was briefly called in ''[[EP102|The Mystery Menace]]'', where Ash used Muk to help him and {{Tracey}} find {{an|Misty}}, {{TP|Misty|Togepi}} and {{AP|Bulbasaur}}, who was kidnapped by a giant {{p|Bulbasaur}} in a sewer. Muk and Kingler also offered to fight for Ash in the Orange Island Championship battle against [[Drake (Orange League)|Drake]] in ''[[EP111|Hello, Pummelo!]]'', but Ash chose {{AP|Tauros}} instead.

Muk was briefly called in ''[[EP102|The Mystery Menace]]'', where Ash used Muk to help him and {{Tracey}} find {{an|Misty}}, {{TP|Misty|Togepi}} and {{AP|Bulbasaur}}, who was kidnapped by a giant {{p|Bulbasaur}} in a sewer. Muk and Kingler also offered to fight for Ash in the Orange Island Championship battle against [[Drake (Orange League)|Drake]] in ''[[EP111|Hello, Pummelo!]]'', but Ash chose {{AP|Tauros}} instead.

[[File:Muk eager to fight.png|thumb|200px|left|Muk asking Ash to let it fight]]

[[File:Muk eager to fight.png|thumb|200px|left|Muk asking Ash to let it fight]]

History

Kanto

Ash's Muk in its debut

Ash caught Muk in the episode Sparks Fly for Magnemite. Ash and his friends were traveling through Gringey City, which was in the midst of a power failure. The local power plant was being overrun by the mysterious Poison-typePokémon, Grimer. After the swarm was located, the Grimer's leader, a Muk, came and challenged the Trainers. However, the vast numbers of Magnemite and Magneton in the city combined attacks to clear out the Grimer, leaving only Muk. With the aid of Pikachu and a Magnemite that was following it due to an electrical build up, Ash defeated and captured the Muk. It was then immediately sent to Oak's lab because its stench was so rancid that it could seep through the Poké Ball. However, Muk's horrid smell seemed to have disappeared in later episodes as neither Ash, nor anyone around him, was affected by it.

Muk was reunited with Ash when he returned home in A Tent Situation. Muk insisted on fighting Team Rocket, and Ash ordered it into battle instead of choosing Bulbasaur. Muk managed to resist Razor Leaf attacks from James's Victreebel, and showed off its newly learned Poison Gas when it bit down on it in an attempt to use PoisonPowder. Lickitung's Lick was even less effective, wiping Muk's face ineffectively to the point of causing pleasure instead of damage. It was then put to sleep by Sleep Powder, but awoke after Gary Oak intervened and drove Team Rocket away.

Muk made an appearance in the special episodes, where it was seen crushing Cassidy, Butch and all of the stolen Poké Balls. It was also seen crushing Tracey when he opened the door to Oak's Lab to Delia.

Best Wishes series

Personality and characteristics

Ash's Muk showing affection for its Trainer and Oak

Ash's Muk is an extremely happy and affectionate Pokémon. It grew an attachment in particular to Professor Oak and as a recurring gag, it would always smother the Professor whenever Ash would make a call to the lab. This was first seen twenty episodes after its capture, in Who Gets To Keep Togepi?. Muk tackled Professor Oak in excitement in Showdown at the Po-ké Corral, when Oak explained that Muk and Krabby had become just like him from its long period of living with him.

Muk loves humans and it's not too particular what kind.

Muk's affection also extends to his Trainer, second in enthusiasm only to Bayleef, despite only having fought for him on three occasions. Muk obligingly crushes Ash in excitement whenever Ash returns to the lab or summons it to his party. Its affection also extends to complete strangers, as was seen when it completely ignored Jessie's Lickitung in order to hug her, also smothering James's Victreebel in excitement. It also smothered Professor Birch upon meeting him in The Right Place and the Right Mime.

Its affection even extends to antagonists, as seen both in the aforementioned encounter with Jessie and James, and also in a special episode, Showdown at the Oak Corral, when it actually appeared sad that Totodile drove Butch and Cassidy away. As Professor Oak said to Jessie, Muk loves humans, and it is not very particular to which kind.

Muk differs from most of Ash's other Pokémon in that it is a defensive Pokémon, with a low attack power and very few moves used across its entire time on the show. It has never been shown to be damaged by a physical attack, with its opponents' moves always absorbed by its odd body type. Despite being quite powerful and good in battle, it has only ever defeated one opponent, Bellsprout (it was put to sleep by Victreebel and knocked out against Gary without a win).